As of today, the iPhone version of the music streaming service is available for download from Apple’s official App Store — UK, Sweden, Spain, France, Norway and Finland only (with the U.S. debut planned for sometime next year) — while a mobile client for the Google-led Android has also launched. The app is free for either platform but you’ll need to be a Spotify premium subscriber — £10 per month in the UK — to access the service.

The key feature that sets Spotify apart from other music streaming services is the ability to play any track or album on-demand rather than at random within a particular genre or ‘artists similar to’. While the mobile version also one-ups its competitors by offering an off-line mode that caches play lists for when your phone is out of coverage or wireless is switched off. This means users can access the service while on the subway or a plane, for example, or utilize the feature to conserve battery life.

As I predicted, however, the iPhone version of Spotify has one major floor. Music can not be played in the background if a user switches applications. Not the fault of Spotify but a limitation imposed by Apple with relation to multitasking on the iPhone. Unsurprisingly, the Android version doesn’t suffer the same fate.

The is the first phase of Spotify’s ambitious mobile plans, with a version for Symbiam S60 (Nokia etc.) next, and a rumored tie-in with Hutchison Whampoa-owned carrier 3 and INQ Mobile, makers of the so-called Facebook and Twitter phones. The Really Mobile Project recently reported that Hutchison Whampoa “head honcho” Li Ka-shing has invested in Spotify and that INQ CEO Frank Meehan now sits on Spotify’s board.

last100 is edited by Steve O'Hear. Aside from founding last100, Steve is co-founder and CEO of Beepl and a freelance journalist who has written for numerous publications, including TechCrunch, The Guardian, ZDNet, ReadWriteWeb and Macworld, and also wrote and directed the Silicon Valley documentary, In Search of the Valley. See his full profile and disclosure of his industry affiliations.